The present invention is related generally to inkjet inks used in inkjet printing, and, more particularly, to the generation of a colorant set derivatized with crown ethers that promote water solubility of the colorant, increase the interaction of the colorant with the media to produce greater durability, and to interact with a reactive fluid to produce insoluble colorants on the media.
There have been many different approaches and attempts to improve lightfastness, smearfastness, smudgefastness and waterfastness in inkjet printing fluids. Some of these approaches include:
Use of Acid-Based Underprinting Fluids: This approach immobilizes dyes based upon their pKa using standard acid/base chemistry. The problem with this approach is that the use of acids can affect the lightfastness of the printed material as well as degrade the media upon which the print is placed. Examples of such an approach are taught in, e.g., U.S. Pat. Nos. 5,181,045; 5,785,743; and 5,679,143.
Use of Cationic Salts in Underprinting Fluids: This approach immobilizes dyes by creating insoluble salts of calcium, magnesium and/or aluminum. Problems associated with this approach include: decrease in the chroma of the printed material due to aggregation of the dyesxe2x80x94requiring much more ink to be placed on the media in order to generate the required chroma, and change in the hue and color characteristics of the dye due to aggregation. An example of such an approach is taught in, e.g., U.S. Pat. No. 5,428,383.
Use of Pigmented Inks: This approach leads to inks which have tremendous properties in all desired areas, that is, lightfastness, waterfastness, and smearfastness. However, with smaller drop volumes, these inks have problems generating the appropriate chroma needed for the marketplace, especially with fast printing applications. Furthermore, stability of the inks tends to be a problem, with pigments aggregating with themselves to generate larger particle sizes.
Although there are no examples of using dyes or pigments for inkjet printers containing crown ethers covalently bound to them, there are several pertinent references that apply to the idea on which the present invention is based:
U.S. Pat. No. 5,516,864 details the synthesis of novel sensors for ions that are based upon the combination of xanthylium-based dyes with N,Nxe2x80x2-diaryldiaza crown ethers which fluoresce in the presence of certain ions. It is used as a sensor.
U.S. Pat. No. 5,134,232 describes the synthesis of novel sensors for ions that are based upon the combination of fluorescent chelator compounds to be used as biochemical sensors for ions.
U.S. Pat. No. 5,891,956 depicts the use of crown ethers for the solubilization of polymers and their subsequent use for the chelation of ions.
U.S. Pat. No. 5,865,994 describes the synthesis of bifunctional crown ethers for the purpose of selectively binding cations for use in quantitative detection of such cations and their separation from similar cations through the use of HPLC (high performance liquid chromatography).
Finally, U.S. Pat. No. 4,790,880 discusses the use of crown ethers used in inkjet inks to form complexes with cations associated with anionic dyes; the ink composition evidences reduced crusting, increased fade resistance, and reduced kogation in thermal inkjet printers.
There remains a need for inkjet inks having improved lightfastness, smearfastness, smudgefastness and waterfastness that employ water-soluble colorants that interact with the media and/or with a reactive fluid to generate durable print images.
In accordance with the present invention, an inkjet ink is provided that employs one or more colorants which are derivatized with one or more crown ethers to render a colorant soluble in water and in water-miscible organic solvents commonly employed in inkjet printing, particularly thermal inkjet printing.
The inkjet ink comprises a vehicle and at least one crown ether derivatized colorant. The colorant may comprise one or more water-soluble or water-insoluble dyes or pigments.
Also in accordance with the present invention, a method of rendering a water-insoluble colorant soluble in an aqueous environment, comprises:
providing a water-insoluble colorant selected from the group consisting of insoluble dyes and pigments; and
reacting the water-insoluble colorant with at least one crown ether.
Further in accordance with the present invention, a method of forming an inkjet ink comprising a vehicle and a water-soluble colorant selected from the group of crown ether derivatized dyes and pigments is provided. The vehicle comprises water and at least one water-miscible organic solvent. The method comprises:
providing a water solublized colorant selected from the group of reactive dyes and/or pigments which have been derivatized with one or more crown ethers; and
adding the crown ether derivatized colorant to the vehicle to form the inkjet ink.
The resulting inkjet ink evidences improved lightfastness, smearfastness, smudgefastness and waterfastness, compared to inkjet inks containing water soluble colorants that are not so derivatized.